Almost all of the main characters in The 100 had a narrative that significantly changed them and played an essential role in their development. At the end of the series, the significant moments could be pointed out as an event that changed everything.
Raven comes to earth
The appearance of Raven (Lindsey Morgan) creates several key events in The 100, such as the destruction of the radio by Bellamy Blake (Bob Marley), who played a role in the sacrifice of the ark, and the brilliant mind of Raven coming to the rescue in more than one occasion.
While at The Ground, Raven (Lindsey Morgan) is an essential player in the name of survival as she helps create weapons for criminals to defend against the Grounders.
Octavia leads the bunker
Octavia (Marie Avgeropoulos) was already facing an identity crisis before having to lead the Second Dawn Bunker. However, being placed in a position of power was not something Octavia expected.
Being in charge of the bunker changed Octavia in a way she couldn’t have predicted, and brought out a dark side of her nicknamed Blodreina. After Earth is destroyed, Octavia has the opportunity to reflect on her past actions and grow from it.
Transcendence is the main plot throughout the seventh season of The 100. With some arguing to become a higher level being and others wanting to continue life as it is, the conflict runs through all the characters.
However, when humanity passes the test, everyone transcends except Clarke but in the last moments of The 100 finale, Clarke learns that transcendence is a choice.
The Being Of Light explains that Madi (Lola Flanery) had chosen to transcend and had no pain, and that the rest of the humans on Earth would not transcend after her death, and that the group would not be able to have children in The 100.